It doesn't look like Mushi-shi Zoku Shou has been licensed in the U.S, so either someone in the U.S has it and just hasn't announced it yet, or it's a world first for Madman. Probably the former.
Edit: I just noticed that English is listed under the language options for Mushi-Shi. Someone in the U.S must have it, as Madman has never produced a dub. Probably either Funimation or Aniplex, as Funi released the first season and Aniplex are streaming Zoku Shou.

It also seems that Hyperdimension Neptunia will be receiving an English dub as well, as English is also listed under its language options.

Madman entertainment have also acquired the rights for the Whole original Sailor moon series as well as Sailor Moon Crystal as well as Love life School Idol Project all for streaming and home release in 2015